Marine Data Literacy 2.0

Providing instruction for managing, converting, analyzing and displaying oceanographic station data, marine meteorological data, GIS-compatible marine and coastal data or model simulations, and mapped remote sensing imagery

 

 

 

 

Home > 9. Operational/Synoptic > 9.2 GHRSST FTP

9.2 Visualizing Historical and NRT Satellite-Measured Surface Temperatures in IDV: GHRSST FTP

  • Exercise Title:  Visualizing Historical and Near-Real-Time (NRT) Satellite-Measured Surface Temperatures in Integrated Data Viewer (IDV): Group for High Resolution Sea Surface Temperature (GHRSST) Products via FTP

  • Abstract:  This exercise demonstrates how to get global, remotely sensed SST data products in easily usable grids (i.e. L3 or L4 NetCDF).  the principal method is via full file downloads, followed by standard visualization methods in IDV.  Users can optionally subset the grids in IDV for easier use, and economical local storage.  The emphasis of this exercise is to provide real-time (or very nearly so) products.  But the GHRSST project system also supports historical data, through the same technical system.  Users of both operational and historical data can refer here to the very best international sources and products.  In all cases, the data must be downloaded via FTP methods.  As various product systems evolve toward direct connection, via OPENDAP technology, they will be migrated to their own, separate MDL exercises.

    • MUR SST products are covered elsewhere because they are available through OPENDAP and they are often provided one day faster than the methods used below.  The choice is up to you, depending on what you need.

    • G1SST products are covered elsewhere because they derive from a blend of satellite, in-situ and modeled results

  • Preliminary Reading (in OceanTeacher, unless otherwise indicated):

  • Required Software:

  • Other Resources: 

  • Author:  Murray Brown

  • Version: 9-28-2015

1.  Open the GHRSST website, and take some time to read through this very useful program.

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2.  Select PRODUCTS & SERVICES to see what's available.
3.  The GHRSST provides both historical data and operational data, which only you can decide to follow.  Here in MDL we'll go after the operational data, because this is the OPS section of MDL.  The same methods pertain to the historical data.

4.  If you click on HISTORICAL DATA, you'll find this list of robust sources.  It seems that all desirable methods are available for you.  The best method, OPENDAP, is not available for us below, so be prepared for the old traditional data download method.
5.  And here's the list of methods to get REAL TIME DATA.  Spend some time here and follow these links.  Try to get your own impressions of exactly what's there and how the methods are presented.
6.  Concerning these apparent 5 routes to the data, fully named in the NOTES above, we have these comments:
  • GHRSST MMR System - This is just a link to pass you off to a separate JPL catalog of many of the same access methods mentioned on the referring page (including the FTP).  It includes a link to an "OPENDAP Interface" to GHRSST products, which does publish usable URL's for use in IDV.  But unfortunately many of them are for dates up to 2 months prior, so this is not a reliable source for true operational purposes.
  • GDAC FTP Site - The old tried-and-true method to download files from a (hopefully) well-organized archive.
    • We'll pursue this method for everything except the MUR and G1SST products, covered elsewhere in MDL by valid OPENDAP methods
  • RDAC Local Servers - Not further followed by MDL
  • HR-DDS Data Granules - Not further followed by MDL
  • MDB Records - Not further followed by MDL

The author hopes that someday, ALL these products will be available via reliable OPENDAP service.  But for now, we'll have to focus on the GDAC FTP Sites.
7.  Here's the route we'll follow to the data, in MDL.  You are encouraged to explore everything on your own later.  Basically, we want fully developed grids (L4) of the whole earth (GLOB), that are near-real-time (NRT).
  • FTP (be adventurous, explore them all!)
    • GDS2
    • L2P
    • L2P GRIDDED
    • L3P
    • L4
      • AUS
      • GAL
      • MED
      • NCAMERICA
      • NSEABALTIC
      • NWE
      • GLOB
        • JPL
          • MUR - Covered elsewhere in MDL
        • JPL_OUROCEAN
          • G1SST - Covered elsewhere in MDL
        • EUR - Not NRT
        • REMSS - Not NRT
        • ABOM
          • GAMSSA 28km - Global file labeled "Sep 27" on Sept 27; see below
        • NAVO
          • K10 SST - Global file labeled "Sep 26" on Sept 27
        • NCDC
          • AVHRR OI - Global file labeled "Sep 26" on Sept 27
        • UKMO
          • OSTIA - Global file labeled "Sep 26" on Sept 27
8.  Download the 4 bottom zipped files to a convenient location, e.g. LIBERIA > DATA > OCEAN > GHRSST
9.  Run IDV.
10.  Select DATA CHOOSERS > FILES than navigate to the files folder.
11.  Select all the files you want to show.  It is very important to specify the Data Source Type, because these are zipped files.

Then click ADD SOURCE.
12.  Now you have the files ready to work with in IDV.  Right-click on the first one, and select PROPERTIES.
13.  First, to keep track of which file this is, select the PROPERTIES tab, and change the name to something simple and logical, as you see here.

In real work, you should use a longer name to identify the date, etc. etc.
14.  Second, (because these are global files) we need to select SPATIAL SUBSET.  Draw an arbitrary square over the Atlantic to activate the tool.

Then enter the desired Liberia values in the tool, as you see here.

15.  Now you can make these choices for a good visualization; try other options on your own, later.  Click CREATE DISPLAY.
16.  Above, you named the data file.  To name the actual display image, use these two steps.  Select EDIT > PROPERTIES.
17.  Then select DISPLAY LABEL and enter a good logical name.  Here we used the same name as above.

Click APPLY.

This is how to you can make much better labels for IDV, which automatically makes names that are usually too long and don't differentiate very well.

18.  Now you have a well named, clear visualization of the ABOM temperature grid.
19.  In real-world work you might want to compare the 4 grids, which you can do later on your own.  To do this, all 4 grids must be displayed with the same temperature value ranges.  Here's how to do that.
20.  Go back to the PROPERTIES tool, and select COLOR TABLE > DEFAULT > CHANGE RANGE.  Enter values that you already know will cover the lowest low and the highest high from all the grids. 

Here we've entered crude guesses of 290 to 305.  [When you see the visual result below, you'll agree the range is too big.]

Then click OK.
21.  You should also use a better palette, and the author recommends COLOR TABLE > DEFAULT > RADAR > DBZ. 
22.  This looks ugly, but it's a good beginning.  Check all 4 grids for the highest high and lowest low, and you'll have a much smaller range to use.  The final images should be much better.
23.  When you have studied these products, you may have favorites, etc.  So make specific plans and methods for capturing and displaying the images you need for your own work.  Assume other students or lab workers will make these, so keep the instructions very clear and logically arranged.